Optimized low heat high performance concrete mixes for DGR shaft sealing

Concrete is expected to be an important part of the shaft seals installed during the decommissioning and closure phase of a deep geological repository (DGR). Concrete structures are presently part of the design for the proposed Ontario Power Generation (OPG) DGR for Low and Intermediate Level Radioactive Waste (L&ILW) near the Bruce Nuclear site, and for the Nuclear Waste Management Organization's conceptual repository design for used nuclear fuel. A low heat high performance concrete (LHHPC) reference mix design was previously developed and key properties evaluated. This paper presents interim results of a program aimed to optimize the LHHPC reference mixture, to fabricate specimens of LHHPC seal materials and to measure key performance parameters. A methodology was developed to design optimized LHHPC mixtures using mix ingredients from local and sustainable sources, which included making changes to the type of cementitious material (CM), CM rate and source, type, source and size of aggregate, type and dosage of super plasticizer, and water to CM ratio. (author)